+$RSYNC -av --existing -f 'exclude,! */' "$from1dir/" "$from2dir/"
+$RSYNC -av --existing -f 'exclude,! */' "$from2dir/" "$from3dir/"
+$RSYNC -av --existing -f 'exclude,! */' "$from1dir/" "$chkdir/"
+$RSYNC -av --existing -f 'exclude,! */' "$from3dir/" "$chkdir/"